Zurich Archivists and Planners Tackle a Growing Duplicate Image Crisis in City Digital Records

City archivists in Zurich confirmed this week that duplicate imagery in the municipal digital records system has reached a scale that is now affecting storage costs and retrieval times across at least three major public databases. The issue, which surfaced publicly during a routine infrastructure review on 30 June at the Stadtarchiv Zürich on Neumarkt, is prompting an accelerated procurement process for automated deduplication software — a move that has drawn both support and scepticism from IT staff inside the administration.

The timing matters. Zurich's city administration has been consolidating its digital infrastructure since 2023 as part of a broader Smart City programme, which funnels digitisation spending through the Amt für Städtebau and partner agencies. As more departments — from the Baugeschichtliches Archiv to the city's planning division at Lindenhügel — migrate decades of analogue material into shared repositories, the volume of accidentally duplicated images has multiplied. A single aerial survey of the Limmatquai district, for example, can generate dozens of near-identical frames that, without automated filtering, are stored as separate files and indexed individually.

What Happened This Week

On Tuesday, staff at the Stadtarchiv completed a preliminary internal audit covering roughly 1.4 million image files uploaded since January 2024. The audit, described in a departmental memo circulated to senior administrators, found that somewhere between 18 and 22 percent of stored files were flagged as potential duplicates or near-duplicates — meaning images that are visually identical or differ only in metadata such as timestamp or file name. That proportion, if confirmed, would translate to significant unnecessary storage expenditure at a moment when the city's IT budget is already under pressure from infrastructure upgrades to the Zürich central data centre on Hagenholzstrasse.

Separately, ETH Zurich's Chair of Information Science published a working paper this week examining how Swiss municipal archives compare with peer cities in Germany and Austria on image deduplication practices. The paper, released through the university's institutional repository, notes that cities of comparable size to Zurich — roughly 450,000 residents — are typically managing between two and five times the storage overhead they would need if deduplication were applied systematically at the point of ingest rather than retrospectively. ETH's findings have added academic weight to what city IT managers have been arguing internally for at least eighteen months.

The practical stakes extend beyond storage bills. The Baugeschichtliches Archiv, which holds photographic documentation of buildings across the city going back to the nineteenth century, relies on fast image retrieval for planning permission reviews and heritage assessments. Duplicate entries slow search results and, in some documented cases, have caused staff to reference outdated image versions when more recent surveys were nominally available in the same system. A planning review in the Aussersihl district earlier this year was reportedly delayed by several days partly because of confusion over which version of a site photograph was current — though the administration has not made a formal statement on that specific case.

What Comes Next

The Amt für Städtebau has indicated it expects to issue a formal tender for deduplication and image management software before the end of August 2026, with a decision anticipated in the fourth quarter. The budget envelope being discussed internally is understood to run into six figures in Swiss francs, though no figure has been officially confirmed. Vendors active in the Swiss public sector market, including several with offices in the Zürich-West tech cluster near Hardbrücke, are already preparing submissions.

For residents and researchers who use the city's online image portals — including the publicly accessible interface of the Stadtarchiv at stadtarchiv.zh.ch — the near-term impact will be limited. Administrators say the existing search interface will remain unchanged during the procurement phase. The more tangible change, if the deduplication project proceeds on schedule, would come in 2027 when a cleaned and rationalised image library could reduce average search return times and make the archive a more reliable tool for historians, architects and journalists working with historical Zurich material. Until then, the city's digital attic stays cluttered.